LYSIANASSIDAE 3I 



on inner margin just below apex. Maxilla 2 slender, inner lobe shorter and narrower 

 than outer, both tipped with setules and rather strong spine setae. Maxilliped with 

 inner plate slender, tipped with three spines ; outer plate large, extending to middle of 

 3rd joint of palp, margin quite smooth and unarmed ; 4th joint of palp well developed. 



Gnathopod 1 simple, stout. Gnathopod 2 much more slender, 6th joint about two- 

 thirds length of 5th, its lower apex produced in a short rounded lobe opposed to the 

 finger. 



Peraeopods 1 and 2 moderately stout. Peraeopods 3-5 very stout, 2nd joints strongly 

 expanded, especially in peraeopods 3 and 4, where they are broader than long, hind 

 margins convex, scarcely notched, in peraeopod 5 oblong, upper and lower hind angles 

 quadrate, hind margin gently convex, slightly notched; 4th and 5th joints also strongly 

 expanded especially in peraeopods 3 and 4 ; anterior margins of 2nd-6th in all three 

 peraeopods strongly armed with spines and spinules. 



Uropod 1 not extending beyond apex of telson, upper outer margin of peduncle 

 strongly spinulose, rami acuminate, outer margin of outer ramus spinulose, and inner 

 margin of inner ramus also, but to a less extent. Uropod 2 with peduncle stout, similar 

 to uropod 1 in armature. Uropod 3 extending to apex of telson, rami ovate, apices 

 subacute, inner margins of both rami with dense fringe of plumose setae, 2nd joint of 

 outer ramus represented by a minute spinule. 



Accessory branchiae developed on segments 2-6, one on each of segments 2-5, two 

 on segment 6. 



In the young specimen (St. 123) pleon segment 3 has a considerably more produced 

 postero-inferior angle, and each lobe of telson has a minute apical spinule. The eyes are 

 smaller and more oval. 



Even the type specimen shows no sign of penial processes or brood lamellae. 



Remarks. This form bears a close general resemblance to Waldeckia obesa, an example 

 of which was caught in the same haul (St. 170), but the relations of the 4th and 5th 

 side-plates and the expanded joints of peraeopods 3-5 at once distinguish it. 



Schellenberg( 1 928, Zool. Anz., lxxix, p. 285), in a preliminary account of Stephensenia 

 haematopus, claims on analogy with the members of the Haustoriidae that the expansion 

 of the joints of the last three peraeopods indicates a burrowing mode of life. Although 

 this feature is rare in the Lysianassidae, it is not unknown, as it occurs in Acidostoma, 

 Menigrates and Onisimus plantus ; in fact the fossorial character of peraeopods 3-5 is 

 better developed in Acidostoma than it is in Stephensenia. 



If the expansion of the joints of the last three peraeopods is really indicative of 

 fossorial habits, the present form must certainly be put in the category of burrowing 

 species. In Acidostoma, however, the mouth-parts are considered (Sars, 1895, p. 38) 

 to indicate a semi-parasitic mode of life. Direct observations are required rather than 

 speculations as to the possible functions of certain features. The nature of the bottom 

 at St. 170 is given as "rock," and at St. 123 as "grey mud." 



